Re: Gigabyte GA-X58A-UD3R (Rev. 2.0) - Realtek ALC889 Static and Noise Issue
This is definitely interferance form other hardware in the machine. I've had this kind of thing on every single system I've owned with integrated sound, on many brands of board.
The problem is, the amount of EMI shielding that the onboard sound has is exactly zero. The reason that the interferance is different or even not present in some situations is down to the fact that each application will cause the system to draw/use differing amounts of power, access other MOBO systems in different patterns etc, meaning that the EMI is forever changing in its main sorce and intensity. Even shielded cards suffer to some extent, as you have seen with the X-Fi.
It could be a dodgy PSU or GPU etc, but I doubt it. It's just par for the course when it comes to cheap onboard solutions. Some cards like ASUS's XONAR range (the top spec cards that is) do offer much more robust shielding both in the form of metal casings around components to physically shield them and in the form of more/higher quality capacitors to smooth and buffer any distortion.
Also worth noting that you should always use the sound card's hard wired phono ports if possible. Your front case jacks are connected by a cable that also has relatively poor shielding and this may even sometimes need to be run over the board to reach the output on it, introducing even more noise to the signal.
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